Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$197.32	9.151%	$215.3768	$215.38	$215.40	$215.40
Purchase #2	$158.94	3.599%	$164.6603	$164.66	$164.65	$164.70
Purchase #3	$212.42	13.719%	$241.5619	$241.56	$241.55	$241.60
Purchase #4	$235.96	12.829%	$266.2313	$266.23	$266.25	$266.20
Purchase #5	$242.47	10.289%	$267.4177	$267.42	$267.40	$267.40
Purchase #6	$240.82	6.105%	$255.5221	$255.52	$255.50	$255.50
Purchase #7	$7.85	8.216%	$8.495	$8.50	$8.50	$8.50
7 purchase totals =	$1,295.78		$1,419.2651	$1,419.27	$1,419.25	$1,419.30